ES2403854T3 - Procedure for the hydrogenation of alkylaryl ketones - Google Patents

Abstract

A process for hydrogenation of alkylaryl ketones to alkylaryl alcohols, a process that involves contacting a feed comprising alkylaryl ketones and 1.0 to 30% by weight of phenoly / or ethylphenol with hydrogen in the presence of a heterogeneous hydrogenation catalyst.

Description

Procedure for the hydrogenation of alkylaryl ketones.

The present invention corresponds to a process for the hydrogenation of alkylaryl ketones.

Background of the invention

Methods for hydrogenation of alkylaryl ketones to alkylaryl alcohols are well known in the art. Processes of this type conventionally comprise hydrogenation of alkylaryl ketones to the corresponding alkylaryl alcohols by contacting the alkylaryl ketones with hydrogen at elevated pressures and temperatures in the presence of a heterogeneous catalyst containing one or more metals that are selected from groups IA, IIB, VI and VIII of the periodic system, as defined on pages 1-11 of CRC Handbook of Chemistry and Physics, 72nd Edition, 1991.

For example, EP-A-0714877 describes a process for producing! -Phenylethyl alcohol by hydrogenation of acetophenone, which uses a copper-based catalyst containing at least one alkaline earth metal carbonate and / or at least one metal compound alkaline earth, said catalyst being reduced by hydrogen before use. Generally, under the conditions that are applied in the hydrogenation, part of the desired alkylaryl alcohols that are formed is dehydrated to arylalkene, which subsequently reacts directly with hydrogen to the corresponding alkylated aryl compound. Dehydration becomes more pronounced with increasing temperature. On the other hand, the catalysts that are usually used become more active at a higher temperature. The operation at a higher temperature, while allowing a higher conversion of alkylaryl ketones, reduces the yield of the desired aryl alcohols, and thereby the selectivity of the reaction. At lower temperatures, the activity of the catalysts with respect to the conversion of alkylaryl ketones is limited, and with it the possible yields. Therefore, it would be very desirable to have the possibility of making the process for the hydrogenation of alkylaryl ketones to aryl alcohols work at lower temperatures while also obtaining high yields of the desired products.

GB-587,181 describes a process for the hydrogenation of acetophenone to phenyl methyl carbinol (C6H5-COH-CH3), ie 1-phenyl-1-ethanol which is not a phenolic compound. US-2,575,403 and ES461 521 also describe the presence of phenyl methyl carbinol, but neither discloses the presence of any phenolic compound.

US 4,208,539 discloses a catalyst for the liquid phase hydrogenation of acetophenone to phenyl methyl carbinol. JP-56.131541 discloses a process for the liquid phase oxidation of secbutylbenzene in the presence of a catalyst to acetophenone, which is then contacted with hydrogen gas in the presence of a catalyst to form alpha-methylbenzyl alcohol. GB-664,851 discloses the preparation of aniline by hydrogenation of nitrobenzene in the presence of a catalyst without alkali.

GB-320,638 discloses the treatment of dioxidiphenylmethane with hydrogen, either at a temperature above the decomposition point in the presence of a normal hydrogenation catalyst or at a temperature below the decomposition point with subsequent addition of a structure catalyst porous US 4,418,005 discloses an orthoselective methylation catalyst for phenol methylation by pressure application.

Summary of the Invention

Surprisingly, a process has now been found that gives improved yields of the desired aryl alcohols at lower temperatures. Accordingly, the present invention corresponds to a process for the hydrogenation of alkylaryl ketones, a process comprising contacting a feed comprising the alkylaryl ketones and 1.0 to 30% by weight of phenol and / or ethylphenol with hydrogen in the presence of a heterogeneous hydrogenation catalyst.

Detailed description of the invention

Within the context of the present application, hydrogenation is understood as the chemical reaction of alkylaryl ketones with molecular hydrogen in the presence of a suitable catalyst, as described, for example, in Ullmanns' Encyclopedia of Industrial Chemistry, 5th Edition, Volume A13, pages 407-410. In this reaction, hydrogen is added to the double carbon-oxygen bond of the alkylaryl ketones, which thus become the corresponding alkylaryl alcohols. The term "alkylaryl alcohol" describes alkanol! - and / or ∀-aryl, and mixtures thereof.

Phenolic compounds within the context of the present invention are aromatic compounds that contain an aromatic core to which at least one hydroxyl group is directly attached.

Phenol and ethylphenol are phenolic compounds. Phenolic compounds may also be formed during any of the steps of the present process, or they may be part of the feed streams that originate, by

example, from steps (i) to (iv) as described below.

The process employs at least 1.0% by weight, preferably at least 1.3% by weight, more preferably at least 1.4% by weight, more preferably at least 1.5% by weight, and most preferably at least 2.0% by weight of phenol and / or ethylphenol. The present process preferably employs a maximum of 30% by weight of phenol and / or ethylphenol, more preferably a maximum of 28% by weight, more preferably a maximum of 27% by weight, more preferably a maximum of 25% by weight, more preferably a maximum of 24 % by weight, more preferably at most 23% by weight, more preferably at most 22% by weight, more preferably at most 21% by weight, more preferably at most 20% by weight, more preferably at most 15% by weight, more preferably at most 10% by weight, and most preferably at most 5% by weight of phenol and / or ethylphenol.

Suitable hydrogenation catalysts according to the present invention may contain as metal or metal compound at least one metal selected from the group consisting of groups IA, IIB, VI and VIII of the periodic system. Suitable catalysts comprise at least one of the metals or metal compounds that is selected from groups VI, VIII and IB, such as chromium, copper, zinc, nickel, palladium and platinum. Preferably, the hydrogenation catalyst comprises copper and / or palladium as a metal or metal compound, because these catalysts are usually not suitable for hydrogenating the aromatic ring system under the conditions typically used for this process. Accordingly, the present invention preferably relates to a process, wherein the hydrogenation catalyst comprises copper as a metal or metal compound. The most preferred hydrogenation catalysts comprise copper as a metal or metal compound, because catalysts of this type have shown high catalytic activity and selectivity over a long period of operation, and because copper is readily available and at low costs.

A commonly known process in which feedstocks comprising alkylaryl ketones are produced is the preparation of oxirane compounds, for example, in an integrated styrene / propylene oxide monomer process. Preferably, said process involves the steps of:

(i)

contacting a feed comprising alkylaryl compounds with oxygen to obtain a feed comprising alkylaryl hydroperoxides and alkylaryl ketones,

(ii)

contacting the feed obtained in step (i) with an alkene in the presence of a catalyst to obtain a reaction mixture comprising alkylene oxide, alkylaryl alcohol and alkylaryl ketones, and

(iii) removing at least part of the alkylene oxide and the alkylaryl alcohols from the reaction mixture obtained in step (ii) to obtain the feed comprising alkylaryl ketones.

The alkenes used in step (ii) of the process have a linear or branched hydrocarbon chain of 1 to 10 carbon atoms. Preferred alkenes comprise 1 to 8 carbon atoms. More preferred alkenes include ethylene, propylene, n-butylene, isoprene and 1-octene, even more preferred alkenes are ethylene and propylene, with propylene being the most preferred.

Under the conditions of steps (i) to (iii) of the process described above, a part of the alkylaryl hydroperoxide formed is regrouped into the corresponding alkylaryl alcohol and the corresponding alkylaryl ketone. Therefore, the feed obtained from step (iii) comprises alkylaryl compounds and alkylaryl ketones. The feed obtained from step (iii) comprising alcohols and alkylaryl ketones can be subjected to a subsequent process step (iv) for the preparation of arylalkenes. On stage

(iv) the alkylaryl alcohols present in the food are dehydrated to arylalkenes. However, alkylaryl ketones do not react to arylalkenes under dehydration conditions. Accordingly, step (iv) preferably involves the steps of contacting the feed comprising the alcohols and alkylaryl ketones at a high temperature with a dehydration agent, and removing at least part of the arylalkene formed from the feed comprising alkylaryl ketones .

If arylalkene is a desired product, it is therefore of particular interest to convert the alkylaryl ketones into alkylaryl alcohols, which can be converted into arylalkene. This would allow to increase the yield of the desired arylalkenes. The conversion can be achieved by hydrogenating the alkylaryl ketones to obtain alkylaryl alcohol.

Phenol and / or ethylphenol can be added to the feed comprising alkylaryl ketones in a suitable concentration and at any suitable stage in the present process or before. Accordingly, the present invention preferably relates to a process wherein at least part of the phenol and / or ethylphenol is added to the feed comprising alkylaryl ketones. Conventionally, it was thought that these phenolic compounds had to be removed before the hydrogenation treatment in order to prevent the leaching of metal components from the hydrogenation catalysts. The removal of phenolic compounds leads to an additional stream of waste, and reduces the overall effectiveness of the process. In addition, the leaching of metals from the catalysts for prolonged periods of time was considered to reduce the stability and activity of the catalyst. Surprisingly, it has now been found that catalysts are not prone to leaching

under the conditions of the present procedure. Phenol and / or ethylphenol can be added to the feeds at any stage of the procedure, or to the feed prior to the procedure, if required. However, it has been found that it is advantageous to accumulate an adequate concentration of phenol and / or ethylphenol already present as impurities in the feed streams, and / or that are generated as side products in the process by recycling at least part of the product mixtures which are obtained in any one of the steps of the present process. Therefore, in a preferred aspect, the present invention relates to a process that involves the steps of:

(to)

 contacting a feed comprising alkylaryl ketones and 1.0 to 30% by weight of phenol and / or ethylphenol with hydrogen in the presence of a heterogeneous hydrogenation catalyst, (b) removing at least part of the alkylaryl alcohol that is formed in step (a) of a product mixture comprising phenol and / or ethylphenol, and

(C)

 optionally, recycle the product mixtures obtained in stage (a) or stage (b) in whole or in part to stage (a). Recycling of the product mixture of step (b) allows to accumulate and maintain an adequate concentration of phenol and / or ethylphenol without separately adding phenol and / or ethylphenol. If only part of the product mixture obtained in step (a) is recycled, the desired fraction can be separated in any suitable manner known to a person skilled in the art. In step (b), at least part of the alkylaryl alcohols is removed from the feed obtained from step (a). The withdrawal can be carried out by any means of separation known as suitable by a person skilled in the art. The withdrawal can be carried out, for example, by procedures that include distillation or any other physical separation process, or by reacting at least part of the alkylaryl alcohols, for example to arylalkenes and removing at least part of the products that are formed. Therefore, the withdrawal preferably comprises subjecting the alkylaryl alcohols obtained from step (b) to the conditions of step (iv) for the preparation of arylalkenes as described above, or by adding the current obtained in the stage. (b) to the power obtained from stage (iii), and subjecting the combined currents to stage (iv). This involves contacting the feed comprising the alkylaryl alcohols at high temperature with a dehydration agent, and removing at least part of the arylalkene that is formed from the feed comprising alkylaryl ketones.

Suitable substrates for the process of steps (i) to (iv) are alkylaryl compounds. Within the context of the present application, the alkylaryl compounds used are alkylated benzenes in which the alkyl substituents are linear or branched alkyl substituents comprising 2 to 10 carbon atoms, and the corresponding ketones and alcohols. A more preferred alkylaryl compound contains one or two alkyl substituents. An alkylaryl compound containing several substituents has the advantage that it may contain several hydroperoxide groups. However, in view of the potential side reactions, it is preferred that there be no more than three substituents, more preferably no more than two substituents. Although mixtures of different alkylaryl compounds can be used, a single type of compound is preferred so that the process conditions for this specific compound can be optimized. Preferably, the alkylaryl compound is ethylbenzene or cumene, with ethylbenzene being the most preferred. When ethylbenzene is subjected to steps (i) through (iii), a mixture of products comprising acetophenone as alkylaryl ketone and 1-phenyl ethanol as alkylaryl alcohol is formed. Therefore, the present invention preferably relates to a process wherein the alkylaryl ketone is acetophenone. Acetophenone is hydrogenated to 1-phenyl ethanol, which in turn can be converted to styrene by dehydration. Therefore, the present process is preferably part of an integrated process for manufacturing styrene monomer / propylene oxide. Alternatively, the present process preferably refers to an integrated process for the production of propylene oxide in cumene recycle. This integrated process has the advantage that the heat generated in the exothermic stages of the process can be reused for the stages of the process that require energy input. In addition, numerous waste streams can be avoided, and only a limited number of raw materials are required, because waste streams are avoided by accommodating the by-products of each part of the process in the mutual reaction sequences. The addition of phenol and / or ethylene to the feed or accumulation in the feed surprisingly results in a catalyst that has improved activity and selectivity. However, if the concentration of phenol and / or ethylphenol in the feed is reduced during the operation, for example by adding a feed free of phenol and / or ethylphenol to the catalyst, the activity and the selectivity of the catalyst are maintained above the activity original for a prolonged period of time before slowly falling to the original activity level. Therefore, a hydrogenation catalyst having improved activity and selectivity can be prepared with a process comprising the steps of: (a1) preparing a hydrogenation catalyst that is insoluble in the reaction medium, and (a2) contacting the catalyst obtained in step (a1) with a feed comprising 0.5 to 100% by weight of phenol and / or ethylphenol. Reaction medium within the context of the present application means the medium within which the hydrogenation catalyst is prepared and the medium used during the hydrogenation reaction. Insoluble has the meaning that the hydrogenation catalyst barely dissolves or dissociates so that it can promote heterogeneous hydrogenation catalysis. Step (a1) may involve one or more of the precipitation, coprecipitation, mixing, impregnation, drying, calcination, and / or hydrothermal treatment stages. Suitable hydrogenation catalysts comprise, based on the total weight of the catalyst, from 5 percent by weight to 95 percent by weight of metal, calculated as metal oxide. The present invention preferably relates to a process wherein the hydrogenation catalyst comprises copper and / or palladium as a metal or metal compound. Most preferably, the hydrogenation catalyst comprises copper. The hydrogenation catalyst may be

conveniently supported on a support that is insoluble in the reaction medium. The support may consist of any vehicle material known to be suitable for this purpose. A suitable carrier material includes silicates, alumina, chromates, zinc silicate oxides, and mixtures thereof.

Usually, the hydrogenation catalyst is activated by reduction, for example by contacting the catalyst with hydrogen. This can be done during stage (a2) or before. Preferably, the hydrogenation catalyst is contacted with hydrogen before step (a2) of the above process. This can be achieved by subjecting the hydrogenation catalyst obtained from step (a1) to hydrogen, preferably under pressure. Such a treatment results in high catalyst activity during the start-up phase of the hydrogenation reaction.

A suitable hydrogenation treatment that can be used comprises contacting the feed comprising alkylaryl ketones with hydrogen at a temperature of 50 to 250 ° C, more preferably 60 to 220 ° C, even more preferably 70 to 180 ° C, and most preferably 80 to 150 ° C, and a pressure of 0.1 to 100 x 105 N / m2 (bar), more preferably 1 to 50 x 105 N / m2, most preferably 10 to 30 x 105 N / m2. The phase

(a) of the process can be carried out with the catalyst in the form of a suspension, a moving bed or a fluidized bed. However, a fixed bed is preferred for large-scale industrial application. The procedure can be carried out in batch mode, semi-continuously or continuously, the latter being the preferred mode of operation. The liquid feed containing the reactants can be passed through the catalyst bed so that the effluent from the reaction zone is catalyst free. Preferably, the hydrogenation according to the present invention is carried out in a downward flow in parallel gas-liquid stream through at least one filler bed reactor (often referred to as a percolator bed reactor). The process of the present invention can also be conveniently applied to catalysts containing copper already in use for the hydrogenation of alkylaryl ketones. By adding to the feed or accumulation in the feed by recycling an appropriate concentration of phenol and / or ethylphenol, the performance of catalysts of this type can be improved, in particular the catalytic activity at lower temperatures. A process for improving the activity of a hydrogenation catalyst is one that comprises contacting the catalyst with a feed comprising 0.5 to 100% by weight of phenolic compounds. In step (a) the catalysts are preferably used at a temperature of 50 to 250 ° C, more preferably at a temperature of 60 to 220 ° C, even more preferably at a temperature of 70 to 180 ° C, and most preferably at a temperature of 80 to 150 ° C In this process, phenol and / or ethylphenol are preferably used for the activation of hydrogenation catalysts.

The process according to the present invention is further illustrated by reference to the following examples.

Experimental part

The following experiments were carried out in percolator flow in a comparative scale unit comprising a reactor connected to a heating / cooling system, a high pressure feed pump, a high pressure pump to recycle product into the feed, and two vessels (for incoming and outgoing feed streams), and a gas connection connected to hydrogen and nitrogen sources. 126 g (130 ml) of trilobular silicon dioxide extrudates comprising 70% by weight of copper oxide and 5% by weight of calcium oxide were mixed thoroughly with 260 ml of 0 silicon carbide particles, 2 mm The extrudates had an average particle size of 1.6 mm, a specific BET surface area of 14 m2 / g and a pore volume of 0.36 ml / g. The mixture was incorporated into the reactor to provide a bed of catalyst. The empty space that remained above the catalyst bed was filled with 3 mm glass balls to provide adequate fluid distribution. The reactor was first purged with nitrogen at a pressure of 2.3 x 105 N / m2, then the reactor temperature was raised to 130 ° C. Hydrogen was introduced at a concentration of 1% by volume, then the hydrogen concentration was gradually increased to 100% by volume at a rate such that the reactor temperature did not exceed 170 ° C. The temperature was then increased to 175 ° C, where it was maintained for 4 hours. In the following examples, the conversion is expressed as the molar flux of converted acetophenone divided by the molar flux of acetophenone supplied in the feed multiplied by 100 to have% in the specified time.

Comparative Example 1

The reactor temperature was reduced to 80 ° C, and the hydrogen pressure was increased to 25 x 105 N / m2. A liquid feed free of phenolic compounds and composed of 57% weight / weight of acetophenone, 4% weight / weight of 1-phenyl ethanol was added to the reactor; 20% weight / weight of 2-phenyl ethanol and 19% weight / weight of other aromatic compounds at a feed rate of 75 ml / h. A liquid product recycle was applied to the reactor at a 4: 1 recycle / feed ratio that resulted in a liquid hourly space velocity of 3 l / l catalyst / hour. After stabilization of the system for 1900 hours, a sample was taken to determine the conversion of acetophenone. It was found that the conversion of acetophenone was 76%.

Example 1

Comparative Example 1 was repeated, but after 1900 hours of operation as described in Comparative Example 1 the liquid feed was changed to a feed comprising 57% weight / weight of acetophenone, 4% weight / weight of 1-phenyl ethanol; 20% weight / weight of 2-phenyl ethanol and additionally containing 2%

5 weight / weight of phenol, the rest being other aromatic compounds. After the 20 hour operation, the conversion of acetophenone was determined to be 87%, and after 250 hours the conversion was determined to be 90%. After switching back to a liquid feed as used in Comparative Example 1 that was free of phenolic compounds, the conversion decreased very slowly over a period of 200 hours to the value of Comparative Example 1.

The comparison of the catalyst of Comparative Example 1 clearly shows that a catalyst with increased activity has been formed. The high stability of this catalyst formed in-situ was further illustrated by the slow degradation to the level of conversion in the absence of phenolic compounds.

Claims (4)

1. A process for hydrogenation of alkylaryl ketones to alkylaryl alcohols, a process comprising contacting a feed comprising alkylaryl ketones and 1.0 to 30% by weight of phenol and / or ethylphenol with hydrogen in the presence of a heterogeneous hydrogenation catalyst.

A method according to claim 1, wherein the hydrogenation catalyst comprises copper as a metal or metal compound.

3. A process according to claim 1 or claim 2, wherein the feed comprising the alkylaryl ketones is obtainable by a method involving the steps of:

(i)

contacting a feed comprising alkylaryl compounds with oxygen to obtain a feed comprising alkylaryl hydroperoxides and alkylaryl ketones,

(ii) contacting the feed obtained in step (i) with an alkene in the presence of a catalyst to obtain a reaction mixture comprising alkylene oxide, alkylaryl alcohol and alkylaryl ketones, and (iii) removing at least part of the alkylene oxide and the alkylaryl alcohols from the reaction mixture obtained in step (ii) to obtain the feed comprising alkylaryl ketones.

4. A process according to any one of claims 1 to 3, wherein at least part of the phenol and / or ethylphenol is added to the feed comprising alkylaryl ketones.

5. A method according to any one of claims 1 to 4, a process that involves the steps of: (a) contacting a feed comprising alkylaryl ketones and 1.0 to 30% by weight of phenol and / or ethylphenol with hydrogen in the presence of a heterogeneous hydrogenation catalyst, and 20 (b) withdrawing at least part of the alkylaryl alcohol that is formed in step (a) of a stream comprising phenol and / or ethylphenol. 6. A process according to any one of claims 1 to 5, wherein the alkylaryl ketone is acetophenone.